This disclosure relates to portable truck or trailer bed ladders that facilitate a user's access to the bed for loading and unloading. The bed of a truck or trailer can often be about five feet above the ground surface, making it difficult for the operators to climb on and off the bed during loading and unloading without the aid of a ladder. Some trucks and trailer beds have permanently mounted step rails positioned for this purpose. However, a permanently mounted step rail must be mounted so as not to increase the overall width of the trailer in order to comply with highway regulations. Therefore, such step rails are usually positioned vertically beneath the outer edge of the truck frame, which can make it difficult to use them for climbing onto and off of the bed. For safe and convenient ease of access, it is desirable that an access ladder be positioned at an angle that is less than vertical extending in a direction away from the bed. It is also desirable that the ladder be portable so that it can be used at many locations around the trailer bed. Frequently, the trailer has a partial load that can prevent easy access to the trailer bed where the partial load is located. In such circumstances the portability of the ladder is particularly desirable. It is also desirable that the ladder be capable of convenient stowage when not in use.